Geochemical signatures of rare earth elements and yttrium exploited by acid solution mining around an ion-adsorption type deposit: Role of source control and potential for recovery

Haiyan Liu (1) , Huaming Guo (2) , Olivier Pourret (3) , Zhen Wang (1) , Maohan Liu (1) , Weimin Zhang (1) , Zebing Li (1) , Bai Gao (1) , Zhanxue Sun (1) , Pierre Laine (3)

1 East China University of Science and Technology
2 China University of Geosciences [Beijing]
3 AGHYLE - Agro-écologie, Hydrogéochimie, Milieux et Ressources

Elevated concentrations of rare earth elements and yttrium (REE + Y) in acid mine drainage (AMD) attract worldwide attention. However, the source and control of REE + Y distribution patterns in AMD remain unclear. Water, rock, sediment, and sludge samples were collected from an ion-adsorption deposit site to investigate REE + Y concentrations and distributions. The heavy REE (HREE)-enriched patterns of the AMD resulted from preferential desorption of HREE in the clay-rich sediment strata, from which the REE + Y were ion-exchanged by an in-situ underground leaching process using ammonium sulfate brine. Free ions and sulfate complexes preserved REE + Y patterns and facilitated REE + Y mobility in the AMD leachate system. High concentrations of REE + Y occurred in the AMD, and decreased progressively through nitrification-denitrification and coagulation-precipitation procedures in a water treatment plant. Concentrations of REE + Y were one to three orders of magnitude higher in AMD than those in groundwater, and were negatively correlated (r2 = −0.72) with pH (3.8 to 8.7), suggesting that an acid desorption from minerals contributed the REE + Y to the AMD from the source rock. Normalized REE + Y patterns showed enrichments of HREE over light REE (LREE) and negative Ce anomaly. The distribution patterns were relatively constant for all water samples, despite their huge difference in REE + Y concentrations. This suggested a limited impact of preferential precipitation of LREE over HREE on REE + Y fractionations during neutralization. The potentially recoverable LREE and HREE were calculated to range between 1.12 kg/day and 3.37 kg/day, and between 1.29 kg/day and 3.76 kg/day, respectively. The findings reported in this study lend promise for efficient REE + Y recovery from AMD

Mots clés: Lanthanide; Acid mine drainage; Water-rock interaction; Fractionation; Critical metals

Domaines: Géochimie

Haiyan Liu, Huaming Guo, Olivier Pourret, Zhen Wang, Maohan Liu, et al.. Geochemical signatures of rare earth elements and yttrium exploited by acid solution mining around an ion-adsorption type deposit: Role of source control and potential for recovery. Science of the Total Environment, 2022, 804, pp.150241. ⟨10.1016/j.scitotenv.2021.150241⟩. ⟨hal-03340094v2⟩